The present invention relates to a buffer memory device and a display drive device, and it relates to a technique useful in application to e.g. a buffer memory of a driver IC (Integrated Circuit) of LCD (Liquid Crystal Display).
To execute a process of data supplied in blocks in each predetermined cycle and another process in the predetermined cycle, the steps of temporarily writing the data supplied in blocks into a buffer memory, reading the written data at a speed faster than a write speed for processing, and executing the other process in a remaining time may be carried out. For instance, an LCD driver IC adaptive to touch detection on a touch panel as well as display driving on a liquid crystal display panel is required to intermittently perform the actions for display and touch detection in each display frame period. So, such LCD driver IC needs a buffer memory for storing display data. It works well as long as the buffer memory has a memory capacity enough to store image data of one display frame.
However, in recent years there has been a strong demand for reduction in the chip footprint of IC—a semiconductor integrated circuit and therefore, the reduction in the memory capacity of a buffer memory has been progressing as well. On the other hand, the circumstance that even if the memory capacity of a buffer memory is reduced, the write of data supplied in synchronization with an action of a host device, and the data read in synchronization with an action in IC are conducted in asynchronization with each other remains unchanged from that before the reduction in the memory capacity.
It is already disclosed that data read from a buffer memory is made faster than data write to make the memory capacity of the buffer memory smaller than a data amount of a display frame. This is described in e.g., the Japanese Unexamined Patent Application Publication No. JP-A-2003-216136.